N-chloroimides, in general, have long been recognized as reagents useful in reactions requiring a source of positive chlorine. Examples of such reactions are, for example, oxidation of alcohols, sulfides, amines, and imines; chlorination of amines, reactive aromatic systems, carbonyl compounds having .alpha.-hydrogens, and the like. Publications which describe such reactions include R. Filler, Chem. Revs. 63, 21 (1963); and R. Stroh, "Methoden der Organischen Chemie" (Houben-Weil), Vol. 5, Part 3, pp. 760-762, 796 et seq., Georg Thieme Verlag, Stuttgart (1962).
Recently, it has been discovered that a penicillin sulfoxide can be converted to the corresponding 3-methylenecepham sulfoxide by the following sequence: ##STR1## This reaction is reported in Kukolja et al., Journal of the American Chemical Society, 98, 5040 (1976) and is further elaborated in Belgian Pat. No. 837,040. From the above it is apparent that the reaction involves a two-step sequence. The first step contemplates thermal generation of the sulfenic acid which then is trapped by oxidation to the sulfinyl chloride. The sulfinyl chloride, in the second step, then, is cyclized to the 3-exomethylenecepham sulfoxide using a Lewis acid reagent, in particular, stannic chloride. The first step, formation of the sulfinyl chloride, requires use of a positive chlorine reagent, and, in particular, an N-chloroimide. Particularly preferred N-chloroimides in accordance with Belgian Pat. No. 837,040 include N-chlorophthalimide, N-chlorosuccinimide, and N-chloroglutarimide.
In carrying out the above penicillin sulfoxide reaction, it is desirable to employ an N-chloroimide having certain properties. First, it is desirable to use an N-chloroimide having a level of reactivity which is neither too great nor to small, that is, a level which provides reaction at readily available conditions while being sufficiently unreactive and stable to provide ease of handling and use in the intended reaction. Secondly, it is desirable to employ an N-chloroimide which will produce, as by product, a corresponding imide which is sufficiently insoluble in the reaction system to permit ready removal from the reaction medium and, thus, easy isolation of the desired product.
These properties are provided by the N-chloroimide of this invention which is N,N'-dichlorobicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic-2,3,5,6-diim ide and which has the following structure: ##STR2##